1. Technical Field of the Invention
This invention relates to a hydraulic pressure takeout apparatus for a tractor to which a hydraulic working implement may be coupled. More particularly, the invention relates to an apparatus for taking hydraulic pressure for driving a working implement from a tractor including a hydraulic device having right and left lift arms for raising and lowering the working implement.
2. Prior Art of the Invention
The technique of providing a hydraulic pressure takeout apparatus for a tractor including a hydraulic device having right and left lift arms for raising and lowering a working implement is known, for example, from Japanese Utility Model Publication H2-15704 (Utility Model Laying-Open Publication S61-87128: Conventional Example 1) and Japanese Patent Laying-Open Publication H8-280206 (Conventional Example 2).
Conventional Example 1 addresses the problem that the lift arms, top link and mounting bases thereof projecting rearward from the hydraulic device or tractor body are obstructive to operations to connect and disconnect hydraulic hoses of a working implement to/from hydraulic pressure takeout units on the tractor body. To solve this problem, Conventional Example 1 provides a support projecting rearward from an upper rear position of the tractor body and/or the rear surface of the hydraulic device, and hydraulic pressure takeout units attached to the support. The pressure takeout units are disposed between a region of pivotal movement of the top link and regions of pivotal movement of the lift arms.
Conventional Example 2 addresses the problem that, depending on the mounting position of a sub-control valve (valve for hydraulic pressure takeout), a complicated piping is required between this valve and hydraulic ports, which is intertwined with pipings extending to other valves to render a maintenance operation difficult. To solve this problem, Conventional Example 2 provides a flow dividing valve and a roll control valve attached to one side of a cylinder case containing a lift cylinder, and a main control valve for controlling the lift cylinder and the sub-control valve attached to the other side of the cylinder case. With this construction, the hydraulic pipes may have reduced lengths since the control valves are arranged close to the lift cylinder.
Conventional Examples 1 and 2 are useful in themselves, but still leave the following problems to be solved.
In Conventional Example 1, an auxiliary hydraulic control valve is formed integrally with and extending transversely from the left surface of a forward portion of the hydraulic housing (cylinder case) acting as the hydraulic device for raising and lowering the working implement. This control valve and the hydraulic pressure takeout units are connected by right and left pipings. This construction has the following problems:
(1) An operation for arranging the right and left pipings is troublesome. PA1 (2) The right and left pipings are exposed, and mud and muddy water could adhere thereto particularly when the tractor works on wet, soft soil. PA1 (3) The auxiliary hydraulic control valve is disposed in a deep interior of a rear fender, which makes maintenance work troublesome. Maintenance is practically impossible when the valve is covered with mud and muddy water. PA1 (4) Right and left pipings are connected to the sub-control valve. PA1 (5) An operation to maintain the sub-control valve requires connection and disconnection of this valve and the right and left pipings. Such an operation is troublesome particularly when the pipings are bent. Moreover, oil leakage could easily occur from a defective connection.
In Conventional Example 2, the sub-control valve (valve for hydraulic pressure takeout) having hydraulic ports (hydraulic pressure takeout units) is mounted on the upper surface of a rear portion of the hydraulic housing (cylinder case). Thus, the problem (3) of Conventional Example 1 is solved, but the following problems remain:
The problems (1) and (2) remain unsolved.